Islamabad - At least 27 people were killed and around three dozen more injured in ethnic violence in Pakistan's southern port city of Karachi, police and health officials said Thursday.

The clashes between activists of ethnic Urdu-speaking Muttahida Qaumi Movement (MQM) and the minority-Pashtun population erupted Wednesday when gunmen shot dead two MQM supporters in the shanty-town neighbourhood of Khwaja Ajmair Nagri.

The violence later spread to several areas of Karachi, a metropolis of more than 16 million people, and continued early Thursday. Rival armed groups exchanged fire in the streets and torched vehicles and businesses.

Karachi's police chief Waseem Ahmad said 22 people had been killed and more than 30 injured, while the rioters torched 18 vehicles.

However, an official at the town's main Jinnah Postgraduate Medical Centre said the death toll rose to 27 when some victims succumbed to their injuries Thursday morning. Most of the killed were Pasthun.

Authorities have deployed Sindh Rangers paramilitary forces to control the riots.

Educational institutions and businesses in many parts of the city remained closed on Thursday, and public transport also stayed off the roads.

Karachi, which is the country's financial hub, has a long history of ethnic violence between the Mohajir, who migrated from India following the creation of Pakistan in 1947, and Pashtuns, who have moved from the North-West Frontier Province for economic reasons. The Mohajirs are represented by MQM.